This application is related to application Ser. No. 07/901,036, filed on even date, and based on German Patent Application P No. 41 20 382.8; and application Ser. No. 07/901,225 filed on even date, and based on German Patent Application P No. 41 20 380.1.
The present invention relates to a locking arrangement for a selector lever of an automatic motor vehicle transmission. A locking member arranged on the selector lever form-lockingly engages in corresponding indentations of an adjustable pawl when the brake is not operated so that the selector lever is locked in the neutral positions (P and N).
In vehicles having the above-described arrangement, after the engine is started, the selector lever must be moved out of a neutral position {P (Parking) or N} into a driving position in order to be able to drive the vehicle. The vehicle may start to drive, although this is not intended, when, while the engine is running, the selector lever is inadvertently moved from the neutral position into a driving position. An unintended abrupt acceleration may also occur during the warmup phase of the engine, when the idling speed is increased, when the selector lever is brought into a driving position.
In order to avoid such disadvantages, it is known from German Patent Document DE 39 11 570 C1 to provide a locking arrangement for the selector lever of an automatic motor vehicle transmission in which a locking member arranged on the selector lever, in a form-locking manner, when the brake is not operated, engages in corresponding indentations of an adjustable pawl so that the selector lever is locked in the neutral positions {P (Parking) or N}. The adjusting of the pawl takes place by means of an actuating element which, in one embodiment, as a lifting magnet, is connected to an electric circuit controlled by a logic circuit. By means of several sensors and switches, the circuit processes information concerning, for example, driving speed, ignition key position and brake pedal operation.
It is an object of the invention to provide a locking arrangement of the above-mentioned type which permits a secure unlocking even when there are inappropriately high operating forces on the locked selector lever.
This and other objects are achieved by the present invention which provides a locking arrangement for a selector lever of an automatic motor vehicle transmission comprising a locking member arranged on the selector lever, and an adjustable pawl. The adjustable pawl has indentations into which the locking member form-lockingly engages when the brake is not operated so that the selector lever is locked in neutral positions. The pawl has steeply extending flanks which bound the indentations in which the locking member rests when the selector lever is locked and an actuating force is applied to the selector lever. The actuating force is introduced into the flanks of the pawl via contact surfaces of the selector lever at a contact point of the flanks. The flanks determine a substantially horizontal force component and a substantially vertical force component of the actuating force.
The locking arrangement according to the invention permits a secure unlocking when there are high operating forces on the locked selector lever since the locking member is arranged on the selector lever and is provided with contact surfaces and comes to rest in a contact point against steeply extending flanks which bound indentations in the pawl. By way of this contact point, the actuating force applied to the selector lever is introduced into the pawl. On the steep flanks, the introduced force disintegrates into an almost horizontal component pointing in the direction of the pivot of the pawl and into a downward-directed component which acts as an almost vertical supporting force. In this case, the steep flanks have the effect that this supporting force has a low range which is clearly exceeded by the horizontal component. As a result, the supporting force can act upon the components holding the pawl in the locked position only with a low power. As a result, the components can be removed from the pawl by low forces, whereby the pawl, while unlocking the selector lever, disengages from the locking member.
In an advantageous development, convexly curved contact surfaces, together with linearly extending flanks, ensure a single contact point which can be determined precisely with respect to its position. The steep-flanked design has the effect that the horizontal component is relatively large and points past the pivot of the pawl at a narrow distance. The extent of the supporting force is therefore small.
The components which hold the pawl in the locking position are constructed as rollers, one roller acting as a supporting member, which is stationarily arranged in the housing, and a second roller acting as a blocking member, by means of an actuating element being moved from a first position into a second position. In the second position, the respective indentation of the pawl is brought, by means of the actuating element, which may, for example, be a lifting magnet, into an engagement by way of the blocking member with the locking member which locks the selector lever. In this position, the supporting force is supported on the supporting member by means of the blocking member. Because of the small amount of this supporting force, the blocking member can be displaced into the second position by low forces. This is promoted by the development of the locking and the supporting member as low-friction rollers.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.